Process for the preparation of a starch ester, in particular a starch acetate, wherein a starch-based feedstock is reacted with an organic carboxylic acid anhydride in the presence of a catalyst. The reaction of the starch-based feedstock and the anhydride is performed at an excess pressure of about 0.1 to 50 bar in an essentially anhydrous medium containing 10% by weight of water at the most. As catalyst, sodium acetate, sodium hydroxide or sulphuric acid is used, and as the reaction medium, acetic acid or excess acetanhydride is used. By means of the invention, the duration of the esterification reaction can be significantly shortened, the separation of the product can be facilitated, and the recirculation of the waste solutions can be rendered more efficient.